The prior art is replete with examples of man's efforts to combine various materials in order to accomplish specific objectives. The art of metallurgy is no exception. By way of example, but not by limitation, a wide number of compositions of matter have been experimented with in the field of jewelry. Various parameters play a part in the selection of appropriate metals for use in jewelry. For example, cost, melt temperature, recyclability, hardness, ductility, stone setting, polishing, belt soldering, torch soldering, and Tig welding are some of the many parameters that come into play in the selection of various compositions of matter for use in jewelry and elsewhere.
Continuing with the jewelry example, again for the purposes of disclosure and not by way of limitation, a variety of prior art compositions concerning the use of silver in jewelry exist. United Precious Metal Refining Inc. of Alden, N.Y. advertises a type “57” composition that it says is a deoxidized sterling silver designed to achieve maximum hardness and also to eliminate fire scale and porosity. It is said to have a hardness approximately equal to standard sterling silver. The exact composition of type “57” is unknown to the Applicant and said to be “international patent pending.” Applicant has tested this material and found it to be only somewhat tarnish resistant and not to have a hardness required for Applicant's use throughout the jewelry industry.
Additional prior art, of which the Applicant is aware, includes “Sterilite CFN” by the Astrolite Inc. company of Morton Grove, Ill. This material is said to be a 92.5 percent silver alloy that eliminates brittleness and is tarnish resistant. Applicant's testing confirmed that it was somewhat tarnish resistant but that, again, it did not have the hardness required for wide application in the jewelry industry.
Applicant has found no prior art composition that yielded a metal, particularly a silver, that was hard enough to withstand day-to-day wear and tear inflicted by users and which was non-tarnishing. One solution experimented with by the Applicant was simply to make the jewelry thicker so that the metal could pass a “squeeze” test. That is, all of the prior art compositions of silver tested by Applicant failed at least one of the tests applied by Applicant, including the test of durability. Some of the metals produced were so soft, in fact, that the rings could be squashed by hand.
As used herein, the term “hardness” means the property of a composition of material that enables it to resist plastic deformation, usually by penetration. However, the term hardness may also refer to resistance to bending, scratching, abrasion or cutting. The ususal method to achieve a hardness value is to measure the depth or area of an indentation left by an indenter of a specific force applied for a specific time. As is known by those of ordinary skill in the art, there are three principal standard test methods for expressing the relationship between hardness and the size of the impression, these being Brinell, Vickers (DPH), and Rockwell (Rs). For practical and calibration reasons, each of these methods is divided into a range of scales, defined by a combination of applied load and indenter geometry. Hardness conversion between different methods and scales is not an exact thing. Different loads, different shape indenters, homogeneity of specimens all complicate the problem. As a result, all conversions are known to be considered as giving approximate equivalents. Hardness may be measured at any point and after any known treatment such as rolling and annealing, for example only.
Thus, there is a need in the art for providing a high strength, tarnish resistant composition of matter that overcomes the drawbacks and deficiencies found in the prior art.